//https://ncode.syosetu.com/n4830bu/243/
#include "atcoder/all"
using namespace atcoder;
#include <bits/stdc++.h>
using namespace std;

using Mint = modint1000000007;

int main() {
    int N;
    cin >> N;
    vector<int> A(N);
    vector<int> cnt(N);
    for (int i = 0; i < N; i++) {
        cin >> A[i];
        cnt[A[i]]++;
    }
    vector<Mint> dp(N + 1);
    dp[0] = 1;
    for (int i = 0; i < N; i++) {
        for (int j = N - 1; j >= 0; j--) {
            dp[j + 1] += dp[j] * cnt[i];
        }
    }
    vector<Mint> fac(N + 1);
    fac[0] = 1;
    for (int i = 1; i <= N; i++) {
        fac[i] = fac[i - 1] * i;
    }
    Mint ans = 0;
    for (int i = 0; i <= N; i++) {
        ans += dp[i] * fac[N - i] * (i % 2 == 0 ? 1 : -1);
    }
    cout << ans.val() << endl;
}